Thursday, November 20, 2014

"Egalitarians By Definition Lack Wisdom" More on the Misuse of 'By Definition'

Regular readers of this blog know that I respect and admire Dennis Prager: he is a font of wisdom and a source of insight. But I just heard him say, "Egalitarians by definition lack wisdom." That is another clear example of the illicit use of 'by definition,' a mistake I pointed out in an earlier entry. Here are some examples of correct uses of 'by definition':

Bachelors are by definition male

Triangles are by definition three-sided

In logic, sound arguments are by definition valid. (A sound argument is defined as one whose form is valid and all of whose premises are true.)

In physics, work is defined as the product of force and distance moved: W= Fx.

In set theory, a power set is defined to be the set of all subsets of a given set.

By definition, no rifle is a shotgun.

Semi-automatic firearms are by definition capable of firing exactly one round per trigger pull until the magazine (and the chamber!) is empty.

In metaphysics, an accident by definition is logically incapable of existing without a substance of which it is the accident.

In astrophysics, a light-year is by definition a measure of distance, not of time: it is the distance light travels in one year.

By definition, the luminiferous either is a medium for the propagation of electromagnetic signals.

By definition, what is true by definition is true.

Incorrect uses of 'by definition':

Joe Nocera: "anyone who goes into a school with a semiautomatic and kills 20 children and six adults is, by definition, mentally ill."

I hope it is clear why the incorrect uses are incorrect. As for the first Prager example, it is certainly true that some environmentalists are extremists. But others are not. So Prager's assertion is not even true. Even if every environmentalist were an extremist, however, it would still not be true by definition that that is so. By definition, what is true by definition is true; but what is true need not be true by definition.

As for the second Prager example, it may or may not be true that egalitarians lack wisdom depending on the definition of 'egalitarian.' But even if true, certainly not by definition.

So what game is Prager playing? Is he using 'by definition' as an intensifier? Is he purporting to make a factual claim to the effect that all environmentalists are extremists and then underlining (as it were) the claim by the use of 'by definition'? Or is he assigning by stipulation his own idiosyncratic meaning to 'environmentalist'? Is he serving notice that 'extremist' is part of the very meaning of 'environmentalist' in his idiolect?